Phase change materials (PCM) are chalcogenide materials that show a significant change in resistivity between the amorphous (OFF) and crystalline (ON) states. The PCM can change from one phase to another by application of heat. Reversible switching behavior can be achieved by applying low voltage pulses of proper duration (direct heating) across the PCM. Due to this property, PCMs have been investigated for use as Radio frequency (RF) switches and have been incorporated in the design of reconfigurable RF components such as inductors. Phase change chalcogenide compounds have been used in rewritable optical disks and other memory devices.
In recent years the demand for highly reconfigurable radio frequency (RF) systems, capable of operating in the severely crowded and rapidly changing modern commercial and military spectral environment, at a reduced overall component count and with a reduced development cost compared to conventional multi-band radios, has been steadily growing. In this context, the implementation of high quality factor, Q, micro acoustic resonators with monolithically integrated switching and frequency reconfiguration functionalities could dramatically reduce loss associated with the filtering element enabling new radio architectures with enhanced spectrum coverage, whose implementation is currently prevented by the lack of such high performance and intrinsically reconfigurable components.
High Q MEMS resonant devices enable the implementation of low insertion loss filters in a very small form factor. Different MEMS resonator technologies based on electrostatic or piezoelectric transduction have been investigated. Among these, the piezoelectric aluminum nitride (AlN) contour-mode resonator (CMR) technology has emerged as a promising solution in enabling the fabrication of multiple frequency and high performance resonators on the same silicon chip. Nevertheless, the current filtering solutions based on AlN micro acoustic resonant devices cannot be dynamically reconfigured to operate at different frequencies, orders, and bandwidths.